Water tube boiler



July 28, 1931 J. JOHNSON WATER TUBE BQLER Filed Aug- 6. 1928 4 Sheets-Sheet l July 28, 1931. .1. JOHNSON 1,816,780

WATER TUBE BOILER Filed Aug. 6. 1928 4 Sheets-Sheet 2 F2-4 T beweeg@- l -GGQ-e gee @Gee-e9@- ,L e-efe ,fr

July 28, 1931.

J. JOHNSON WATER TUBE BOILER Filed Aug. 6. 1928 4 SheebS-Sheet 3 J Jo hn ScY v /NVSN To@ Wou/4 YM 7/5.

July Z8, 1931. J. JOHNSON WATER TUBE BOILER Filed Aug- 6, 1928 4 Sheets-Sheet 4 Egg.

Patented July 28, 1.931

J' OHN JOHNSON',

F WIMIBLEID'ON, LONDON, ENGLAND WATER TUBE BOILER Application filed August 6, 1928, Serial No. 297,692, and in Great Britain August 15, 1927.

This invention relates to Water-tube boilers and especially to those of the high-pressure marine type burning fuel in the gaseous, liquid or pulverized form.

'if l The main object of the invention is to provide a boiler of the kind indicated which will have a higher thermal efciency and at the same time be smaller, lighter and cheaper than comparable types of boiler which have been applied to marine purposes.

To obtain the object sought, the present invention seeks fundamentally (a) To reduce radiation losses and (b) To obtain low leaving temperatures of the gases in accordance 1&5 with the following general principles, modiiications being made' therein as required to meet particular requirements The volumetric capacity of the combustion chamber for a given duty should be as small asis consistent with the time required to effect complete combustion of the necessary weight of fuel before the gases impinge on relatively cool surfaces; in addition, the form of combustion chamber should be chosen so that the area of its envelope is low in/proportion to the volume in order to approximate to the geometrically ideal but practically unattainable spherical form. Due to the relatively small heating surface of such an envelope, a high furnace temperature'coupled with eflicient heat abstraction from the products of combustion are necessary, these requirements, which are to a certain degree interdependent, being jointly satisfied, in part by highly preheating the combustion air and employing a minimum surplus thereof, in part by passing the gaseous media over the heat-interchange surfaces at a considerable velocity and in part by providing an extended path for the products of combustion.

In order to carry the above principles into effect, the invention consists in a water-tube boiler of the single or divided-flow type for burning fuel in the liquid, gaseous or pulverized form, having an upper and a lower longitudinal drum and tubular side and end walls including banks of outwardly-curved steamgenerating tubes connected to the upper and lower drums along their length, the tubular 50 walls, modified as required for the accommodation of the burners, thus serving as a complete or substantially complete envelope for the chamber in which the fuel is burned.

Referring to the accompanying drawings, which are of a diagrammatic nature Figure 1 shows a sectional end view of one form of boiler according to the present invention;

Figure 2 being a tion;

Figure 3 shows a modified form of boiler provided with an outer supplementary bank of water tubes connecting directly the upper and lower drums; y

1Figure 4 being a corresponding sectional P an;

Figure 5 is a detail of Figure 4 to a larger scale showing a row of small-diameter tubes associated with certain of the main steamgenerating tubes to form a baille, and

igure k-6 a similar detail to show the method of baffling certain of the supplementary water tubes;

y F igure 7 shows a sectional end view of a form of the invention of the divided-floul type; while finally Figure 8 shows a sectional end view of a boiler according to the present invention pro* vided with a modified form of superheater.

The same reference symbols are used in the different ligures to denote corresponding parts, while the arrows show the general .d1 l rection of flow of the hot gases.

In carrying the invention into effect anccording to the illustrative form shown in Figures 1 and 2, the boiler comprises an upper steam-and-Water drum, A, and a lower water drum, B, placed the one above the other with their axes parallel in a vertical plane, the drums being connected along their lengths on the two sides by banks of water tubes, C and D, curved outwardly to a considerable eX- tent, for example, so as roughly to define a cylindrical surface. The drums are further connected at the ends by steam-generating tubes, E, F, curved in a plane transverse to, the length of the drums, and in part overlapping, as shown, to complete the combustion space or chamber. i

The tubes, D, on one side of the boiler, all

corresponding side elevallar example under description,

serve as risers, while the bank of tubes, C, on the other side consists of one or-more rows or risers, c1, and adjacent thereto on the side remote from the furnace further rows of tubes/c2, actingv as downcomers for all the water tubes. y

On the same side of the main water drum,

B, as the downcomer tubes, c2, and at about the same level, is arranged a superheater drum, H, having reversed U-tubes, h, secured thereto, and following approximately the curve of the downcomer tubes, c2, to which they4 are adjacent. Outside, the superheater tubes again is a supplementary water drum, J, connected to the steam-and-water drum, A, by a bank of curved tubes, K, the outer ones, 101, of which preferably act as a feed-water heater and issue from a longitudinal pocket,

within the supplementary drum, J. In addition, a baiile, L, extends downwardly a certain distance from the steam-andwater drum, A, between the downcomer tubes, c?, and the superheater tubes, h, .so that the gases from the furnace pass under this baffle to the superheater tubes, k, and the supplementary bank of water tubes, K, and are thus given a path of considerable length in relation to the tubesover which they pass.

To assist in maintaining the desired high temperature of the furnace, the boiler is encased both at the sides and endsnby walls of rebrick, N, N, screened or partly screened by the water tubes above described, so as to prevent overheating. l

The air for combustion, which preferably does not exceed by more than about 20 per cent. the amount theoretically required, is heated to say 400o or 500 F. in an air prehea-ter, M.

The principles underlying the methods securing a positive circulation last described may be extended by omitting the bank of tubes, K, with supplementary drum, J, shown in Figure l, and substituting therefor the downcomer bank, P, having inner and outer tubes, p1, p2 (see Figures 3 and 4)^arranged outside the superheater and connecting directly the upper and lower drums, A and B. To ensure that all the tubes of the banks, C and D, serve as risers, only one or two rows of tubes are provided as indicated at c1 and (Z1 respectivelyf In addition, in the particulongitudinal banks of tubes, "R, S, also serving as risers are arranged in the combustion chamber.

In order to utilize more adequately the space between the bank of tubes, C, and the outer bank, P, the Us of the superheater may be successively elongated as shown at h1 to h6, while within the smallest U, 71.1, is arranged an obturator body, Q, of {ire-clay or the like to serve as a baffle.

Further, in order to give the desired extended path to the hot gases, a row of small# diameter tubes, c* (see Figure 5) is arranged to the tubes, c1, serving tion gases pass by ways of the v--outside the steam-generating tubes, c1, ad-

]acent to the superheater, this row of small tubes extending for to two-thirds of the length of the boiler from the front end and owing' to ltheir proximity asa baffle; the remaining one-third of the length of the bank of tubes, C, denoted by the numeral, 3, thus forms a. passage for the hot gases. Similarly, a few rows of closelypitched tubes, p1 (see Figure 6),'are arranged on the side of the supplementary lbank of tubesP, adjacent to the super-heater so as to form in effect a baffle extending a two-thirds of the length of the boiler from the rear end leaving a passage of length, 7 atthe front end. In addition, as shown, the longitudinal banks of tubes, R, S, sub-dividing the furnace, stop shortA of the rear end of the yboiler so that gaps, 4 and 5, respectively are left.

With such an arrangement, the combusgaps, 5 and 4, atl the rear end of the banks of tubes, R, S, continue through the passage, 3, at the rear end of the bank, C, and thence pass forwardly through the superheater, being divided into two streams by the rebrick obturator, Q., to correspond more or less to the two legs of the superheater U s; finally, the gases iow through the passage, 7, in the front end of.

the linner tubes, p1, whence they pass rear! wardly and upwardly among the remaining tubes, p2, of the bank to the preheated If desired, a longitudinal pocket, p3, may be arranged in the drum, A, to receive the ends of some or all of the tubes, p2, the feed water being pumped into this pocket to descend in a direction on the whole opposite to the direction of flow of the hot gases.

All the form-s of the invention above described are of the one-sided or single-flow type, i. e., the products of combustion pass to the uptake on only one side of the steamand-water drum. In Figure 7, however, a boiler in accordance with the present invena distance, 2, equal sayV distance, 6, equal to about tion is shown of the double-sided or divided- -flow type, i. e., products of combustion pass shown, the same reference symbols for both the right and left-hand sides being use as for the left-hand side in Figure 3. In the present form of the invention, two malin rows of water tubes, c1, are provided on each side, individual tubes in the neighbourhood of the drums, A and B, between which they are connected, being set or joggled as shown to form baffles so that the gases are directed over the various heat-interchange surfaces in the manner indicated by the arrows. The

` many, if any,

end-wall tubes in this form of the invention may be as shown in Figure 1.

Further, in Figure 7, the combustion chamber is shown divided, by way of example, by two juxtaposed longitudinal walls of tubes, r, s, the tubes of each wall being disposed in a vertical plane.

Referring now tovFigure 8, almodified form of superheater is shown applied to a typical boiler according to the present invention.

According to this form, t, t, forming as it were a superheater element and lying 1n a plane transverse to the axis of the drum, A, leave the latter into which they are expanded and pass down into the hot gases to form a loop, T, preferably turned inwardly towards the furnace as shown; the tubes then return to the steam-and-water drum, A, into which they are expanded and deliver into a. longitudinal internal pocket, U, formed to receive them. The partly superheated steam reverses its direction in this pocket to pass through a second'pair of superheater tubes, 251, downwardly through the hot gases and preferably through a zone thereof nearer to the furnace as shown to form a second loop, T1, and return to a longitudinal internal pocket, V, in the steam drum serving to collect the superheated steam and provided with a valved outlet of any suitable construction.

lt will be seen that the form of superheater just described becomes in eect an integral part of the steam-generating unit, the usual headers and drums in connection with the superheater being eliminated with a consequent gain in space, weight and cost.

ln the examples of the invention above described, the fraction of the aggregate watertube area exposed to radiant heat is larger than usual; further the shape of the combustion chamber is substantially that of a right circular cylinder of comparatively short length thereby giving a small surface in relation to its volume in accordance with the principles set out above, while the tubular side and end walls form a substantially complete envelope of .effective heating surface to the combustion chamber; in addition, the preheater ensures a supply of highly-heated air to the furnace while the products of combustion are drawn over the heat-interchange surfaces, e. g., water tubes, superheater tubes,

' air-preheater tubes and the like, at a considerable velocity by way of defined by the baffles.

uWhen simplicity or cheapness of manufacture is the dominant consideration, only the fundamental structure of the improved boiler need be retained together with as of the high-efficiency adjuncts the conditions of the an extended path as are required to meet particular design.

Although specific examples of the invenapair of tubes,'

bination, an u tion have been described above, it will be understood that many variations can bc made in detail without departure from the general principles outlined above, while structural features shown or described in relation to one form of the invention may be equally applicable to other forms.

aving now described my invention what I claim as new and desire to secure by Letters Patent is l. A water-tube boiler comprising in combination, an upper and a lower longitudinal drum; outwardly-curved oppositely-disposed banks of water tubes connecting said upper and lower drums along their length in wall formation to enclose a combustion chamber laterally; and disposed within said combustion chamber other water tubes in wall formation also connecting said upper and lower drums along their length.

2. A water-tube boiler comprising in combination, an upper and a lower longitudinal drum; outwardly-curved oppositely-disposed banks of water tubes connecting said upper and lower drums along their length in wall formation to enclose a combustion chamber laterally; and disposed within said combustion chamber other water tubes in wall formation also connecting said upper and lower drums along their length, said other water tubes being curved to afford resilience.

3. A water-tube boiler comprising in combination, an upper and a lower longitudinal drum; a plurality ofbanks of oppositely-disposed outwardly-curved water tubes connecting said upper and lower drums along their length in wall formation to enclose a combustion chamber laterally; together with superheater tubes curved to conform with the curvature of said outwardly-curved tubes, said superlieater tubes being disposed between certain of said outwardly-curved banks of tubes.

el. A water-tube boiler comprising in combination, anupper and a lower longitudinal drum; inner and outer banks of outwardlycurved water tubes connecting said upper and lower drums along their length in wall formation, the inner banks enclosing a combustion chamber laterally; and superheater tubes disposed between said inner and outer banks and curved to conform with the curvature of said outwardly-curved tubes, certain tubes of both said inner and said outer banks being closely pitched over a part of the length of the boiler to form a baflle and certain other tubes of both Said inner and said outer banks being spaced .apart over another part of the length of the boiler to form a duct for the furnace gases, said closely-pitched and said spaced-apart tubes in the two said banks being reversely disposed in relation to the length of the boiler.-

5. A water-tube boiler comprising in comper and a lower longitudinal drum, outwar ly-curved oppositely-disposed water tubes connecting said upper and said lower drums along their length in wall formation to enclose a combustion chamber laterally, said outwardly-curved tubes receiving heat only from said combustion chamber; superheater tubes disposed on the outside of certain of said outwardly-curved tubes and curved to conform with the curvature of said tubes; together with other Water tubes connected to at least one of said drums, said other tubes being disposed outside atleast some of said superheater tubes and curved to conform with the curvature of said tubes.

In testimony whereof' I have signed my 11a-nie to this specification.

JOHN JOHNSON. 

